A typical prior art container that stores a substance to be dispensed therein, such as a vial for example, includes a rigid body having a chamber therein for storing the substance to be dispensed. However, when the chamber is sealed, air cannot enter therein to replace the volume of the dispensed substance. Thus, the storage chamber can have a variable-volume storage chamber, in order to reduce the volume thereof with each dispensed dosage and prevent suction forces.
One approach to providing a variable-volume storage chamber is to provide a flexible chamber within the device body, which is deformable with each dispensed dose. However, such a design generally requires additional manufacturing and assembly steps, such as, for example, extruding a chamber parison from a polymer, blow molding the parison into a flexible chamber, and then assembling the chamber within the device body. To avoid the extra manufacturing and assembly steps, and thus, extra expense, several devices utilize the volume within rigid body itself as the storage chamber.
As the rigid body is not deformable, some devices mount a sliding stopper to the body, which is slideable within the body upon dispensing of a dose of substance, to correspondingly reduce the volume of the storage chamber. Some of these devices also fill the chamber through the stopper. One drawback associated with such sliding stoppers is that they may slide while filling therethrough, thereby reducing the volume of the chamber, and reducing the amount of doses than can be filled therein.